1. Field of the Invention
The present invention relates to an apparatus for and a method of reproducing information from an information recording medium, such as an optical disc.
2. Description of the Related Art
In the optical disc represented by a Compact Disc (CD) and a DVD, the long or short length of a pit is used to record information. However, in order to record information for copy control for the prevention of illegal copying or the like, there is a request for reserving another recording area without decreasing a recording capacity by the pit.
As a method of increasing the recording capacity by other means except the method using the long or short length of the pit, there is known a technique of displacing or shifting the position of the pit in the radial direction of the optical disc. This technique is such that information is recorded by wobbling the position of the pit in the radial direction of the optical disc and by performing spread spectrum with respect to the wobble.
Such a method of reproducing the spread spectrum data from the optical disc is disclosed in Japanese Patent Application Laying Open NO. 2003-85896. This technique is such that a clock signal is extracted from a read signal corresponding to the movement of a pit position aside from a read signal obtained by detecting the length of the pit, and that data is reproduced by using the extracted clock signal.
However, the structure of an information reproducing apparatus becomes complicated if the clock signal is reproduced differently from the read signal obtained by detecting the length of the pit. Also if the clock signal is reproduced from the read signal corresponding to the movement of the pit position, it is influenced by the eccentricity of the optical disc, which increases a jitter component and an error rate.